Process of manufacturing paperboard



Patented Get. 1, 1929 UNITED STATES PATENT OFFICE" LEVTS MILLER BOOTH, OF PLAINFIELD, NEW JERSEY, ASSIGNOR OF ONE-THIRD TO ALMERON WICKHAM, OF GLOUCESTER CITY, NEW TO RALPH W. SHAFFER, OF CAMDEN, NEW JERSEY JERSEY, AND ON E-THIRD PROCESS OF MANUFACTURING PAPERBOARD I No Drawing.

This invention relates to a process of manufacturing paper board and the objects of my invention are to insure effective sizing, develop the maximum strength of board and to effect an economy in the use of size and size precipitating chemicals, by so treating the ply next to the sized ply that desizing will not occur.

In the manufacture of some grades of paperboard, for example, container board, the sheet is formed of from five to seven plies which while still wet are consolidated into a single sheet. In some cases the stock used to form one or more of the outer plies, desig- O nated as liners, is sized by the use of an emulsion of resm, and sulphate of aluminum. It

is riot customary to size the inner plies of the board, known as filler, although in some cases some sizing is done.

For the production of a sized board which is acceptably resistant to Water, wherein the size emulsion is precipitated with sulphate of aluminum, it is necessary that the hydrogen ion concentrationbe held within reasonable limits, slightly on the acid side. In other words, if Wide variations of hydrogen ion concentration prevail in the stock from which resin-alum sized paper or board is to be made uniformity of sizing will not be produced, or the strength of the resulting board will be impaired.

In mills where the minimum amount of size and alumare used to effect water proofing of container board, no size or alum is used in the preparation of the tiller stock. Reliance for water proofing is placed on the sizing of the liner.

The filler is usually made of cheaper grades of stock than the liner. Frequently this filler stock. contains matter of alkaline nature. During the formation ofthe board on a multicylinder machine there is an opportunity for the alkaline water which is squeezed from the filler stock to pass to the liner stock and thereby to influence the linerstock, resulting in diminishing the degree of sizing of the board.

on the sized liner by the alkaline water is to Application filed November 27, 1928. Serial No. 322,298.

or acid salt is applied to a water suspension of fibers, the fibers become more acid than the water which may be drained from them.

Since there is no advantage in acidifying the fibers it is apparent that the acidification in excess of that necessary to react with the soluble alkali in the vehicle water is wasted. Moreover, it is detrimental, because of the impaired strength of the board made from acidified fibers.

In the use of my improved process I have found that the necessary acidity may be conveniently applied by the addition of an acid salt either dry or in solution to the alkalinefiller stock just previously to its application to the filler vat or vats next to the liner vat or vats carrying the sized stock, in order to form a protectingply which prevents desizing by the alkalinity of the watersqueezed from the remaining filler plies. In the application of an acid salt, for example,pulverized sulphate of aluminum, I have used a mechanical dry feeder such as is commonly employed for dis-' pensing dry materials. The use of the acid salt at a late stage in the process affords time for reaction with only that portion of the 0bjectionable alkali which is dissolved in the vehicle water and does not contemplate the acidification of the stock which occurs when the acid is furnished to the heaters.

In the manufacture of container board, wherein one liner is sized, I have added the acid salt to the stock entering one filler vat, namely, the vat next tothe sized liner.

My process does not contemplate the use of an acid or an acid salt as a size precipitant, but rather the prevention of desizing action caused by the drainage of soluble alkali from unsized stock into stock which has been sized.

What I claim as new and desire to secure by Letters Patent of the United States is:

1. In the manufacture of multi-ply paper board wherein one or more of the liner. lies are sized, the addition of acidity to sue of the filler stock as is supplied to the filler vat which is next to the liner vat prior tothe delivery of the stock to the paper machine vat.

2. In the manufacture of multi-ply paper board wherein one or more of the liner plies are sized, the addition of acidity to the filler stock after it has left the-Jordan and prior to the delivery of stock to the machine vat.

3. In the manufacture of multi-ply paper board wherein one or more of the liner plies are sized, the addition of'sulphate of aluminum to such of the filler stock as is supplied to the filler vat which is next to the liner vat,

prior to the delivery of-the stock to the machine vat.

n the manufacture of multi-ply paper board herein one or more of the liner plies are sized, the addition of an acid salt to such of the filler stock as is delivered to the paper machine vat which is next to the sized liner stock vat.

LEVIS MILLER BOOTH. 

